The invention relates to the use of a strip for a re-releasable adhesive bond.
German Offenlegungsschrift 33 31 016 discloses adhesive films for re-releasable adhesive bonds which permit an adhesive bond produced therewith to be releasable by pulling on the adhesive film in the direction of the plane of adhesion. Such adhesive films permit high adhesive forces and shear strengths to be obtained and adhesive bonds to be re-released without further aids, comparable to opening a zip fastener or, for even better comparison, to opening a preserving jar: the rubber seal is pulled out of the sealing joint by the tab.
However, serious disadvantages in using such adhesive films have been found in practice. On the one hand the product requires explanation. Someone who has hitherto not used such an adhesive film is readily inclined to adhesively bond the joint parts to one another in such a manner that the adhesive film disappears between the joint parts, no longer projects, and can thus no longer be pulled: this results in an irreversible adhesive bond with corresponding disappointment. However, the disappointment is equally great if, on correct use, the adhesive film tears when pulled: this also results in an irreversible adhesive bond. The advantage of a re-releasable adhesive bond which can be produced in an extremely simple manner without damaging the joint parts just by pulling is transformed into a serious disadvantage, since the joint parts which are to be reseparated are now permanently bonded. Usually the only course that remains is to destroy the joint parts.
The problem of tearing during pulling was also recognised by the inventors of German Offenlegungsschrift 33 31 016, and they paid particular attention to it. Accordingly, on page 4, centre, a specific ratio of pull-off force to tear strength is specified; the tear strength should always be greater than the pull-off force and for safety reasons the ratio of pull-off force to tear strength should be 1:2 to 1:3.
However, it has been found in practice that this precautionary measure is often not sufficient. An adhesive bond of substrates on an open-air exhibition site, which is intended to be reseparated after the end of the exhibition, can, due to tearing, no longer be detached. The same applies to calendars or advent decorations stuck to a window. Posters or pictures, too, similarly fastened to the wall become irreversible wall embellishments as soon as the adhesive film has torn off when pulled. The damage is considerable, the customer lost. The use of even thicker adhesive films as recommended by German Offenlegungsschrift 33 31 016 is also of no help in preventing such tearing.
German Patent 37 14 453 also discloses the use of such an adhesive film, referred to there as strip tape, in order to be able to re-remove practice explosive charges non-destructively from practice objects. A tab 6 is also allowed to project laterally out of the adhesive joint here, so that it can be pulled and the bond thus re-released. In this application, too, tearing often occurs in practice.